Fuel priming pump



March 17, 1970 ,po-r ET AL 3,500,759

FUEL PRIMING PUMP Filed June 13, 1968 INVENTORS MILLARD D. POTTER JOHNH. PARKS ATTORNEYS United States Patent 3,500,759 FUEL PRIMING PUMPMillard D. Potter, Bartonville, and John H. Parks, Peoria, 111.,assignors to Caterpillar Tractor (10., Peoria, 111., a corporation ofCalifornia Filed June 13, 1968, Ser. No. 736,710 int. Cl. F04b 9/22,21/08, 33/00 US. Cl. 103-175 1 Claim ABSTRACT OF THE DISCLOSURE Acompact fuel priming pump having a reciprocable piston within a firstcylinder, a second cylinder concentrically arranged about the firstcylinder to form an annular passage in communicatiton with One end ofthe first cylinder and suitable check valves separately communicatingthe other end of the first cylinder and the annular passage between thetwo cylinders with a fluid outlet and a fluid inlet.

Fuel priming pumps are commonly employed with engine fuel systems todeliver a suflicient quantity of fuel for start-up of the engine. Manyof these priming pumps are of the single action type for example, andwhile being simple in design, do not have the necessary pumping capacityto permit priming of large displacement engines within a short time.Larger capacity priming pumps, for example those with double action orwobble plate design, generally deliver priming fuel at a higher rate.However, these pumps are generally complex in design and are expensivebecause of precision machining requirements. The complex construction ofthe pumps also commonly results in a larger size than is readilycompatible with many engine systems.

Accordingly, it is an object of the present invention to provide acompact, high capacity pump. It is also an object to provide such a pumpwhich is further of simple and economical construction.

The present invention fulfills these objects by arranging a reciprocablemember within a hollow pump body to form two opposing chambers ofvariable volume with check valve means for communicating each of thechambers with a fluid inlet and a fluid outlet. Preferably the hollowpump body is a first cylinder having a reciprocable piston disposedtherein and having a second cylinder concentrically arranged about thefirst cylinder with an annular passage formed between the cylinders forcommunicating a variable chamber at one end of the first cylinder withthe check valve means.

Other objects and advantages of the invention are made apparent in thefollowing description having reference to the accompany drawing.

In the drawing:

FIG. 1 is a side view, with parts in section, of a priming pumpconstructed to the present invention;

FIG. 2 is a view taken along section lines IIII of FIG. 1 illustrating abase member of the pump; and

FIGS. 3 and 4 are views taken respectively along section lines IIl-IIIand IV-IV of FIG. 2 to illustrate internal construction of the basemember.

A fuel priming pump constructed according to the present invention andillustrated in FIG. 1 comprises a plunger assembly 11 arranged forreciprocable motion within a first cylinder 12. The plunger assembly 11comprises an elastomeric piston member 13 in fluid sealing relation withthe inside diameter of the cylinder 12 and a rod member 14 upon whichthe piston 13 is mounted. A second larger cylinder 16 is concentricallyspaced apart from the first or inner cylinder 12 to form an annularpassage 17 between the two cylinders. The upper ice ends of the twocylinders are closed by means of a plug member 18 with the rod member 14penetrating a bore 19 formed in the plug 18. Seal means 21 prevent fluidleakage between the plug and the rod 14. The lower ends of the twocylinders are closed by means of a base member 22 so that a first orlower chamber 23 of variable volume is formed within the inner cylinder12 by means of the base member 22 and the bottom of the reciprocablepiston 13. An opposing or upper chamber 24 is also formed within theinner cylinder 12 by means of the top of the reciprocable piston 13 andthe plug 18. The extended end of the rod 14 is threaded to a resilientknob 26 to permit manual reciprocable operation of the plunger assembly11. The knob 26 is normally secured in a position with the plunger 11depressed within the pump shown in FIG. 1 by means of a spring lock 27which is pivoted at 28 to the outer cylinder 16 and the plug 18. Both ofthe variable volume chambers 23 and 24 are in communication with a fuelsource (not shown) and an engine fuel system (not shown) by means ofcheck valve and internal passages arranged within the base member 22 anddescribed below with reference to FIGS. 2-4. The lower chamber 23 is indirect communication with two of the check valves while the upperchamber 24 is communicated with two additional check valves by means ofa passage 29 formed by the plug 18 and the annular passage 17 betweenthe two cylinders.

Simple and economical constructiton of the present priming pump isapparent from consideratiton of the components described above. Forexample, the cylinders 12 and 16 may be of standard precision t-ubingwhile the plug member 18 and base member 22 are preferably formed withconcentric, stepped surfaces 31, 32, and 33, 34 respectively ofappropriate diameters for pressfit engagement with the ends of the twocylinders 12 and 16, respectively.

Construction of the base member 22 and the arrangement of check valvestherein is more clearly seen in FIGS. 2-4. Referring particularly toFIGS. 3 and 4, the reciprocable piston 13 is in a raised position tosimplify the figures and more clearly illustrate the lower variablevolume chamber 23. A recessed inlet 36 is formed at the bottom of thebase member 22 for communication with a fuel source (not shown). Anotherrecessed passage 37 is similarly formed for outlet communication with anengine fuel system (not shown). Two inlet ball check valve arrangements38 and 39 are in communication with the fluid inlet passage 36 to permitfuel to flow into the pump from the passage 36 when pressure behind thecheck valve is sufficiently reduced. Another pair of outlet ball checkvalve arrangements 41 and 42 are in communication with the outletpassage 37 to permit fluid flow from the pump into the passage 37 whenthe check valves experience a suificient pressure rise within the pump.The inlet check valve 38 and the outlet check valve 41 are in directcommunicatiton with the lower chamber 23 by means of respective passages43 and 44 formed by the base member 22. The inlet check valve 39 and theoutlet check valve 42 are blocked from communication with the lowerchamber 23 while being in communication with the annular passage 17 andthe upper chamber 24 by means of cross-drilled passages 46 and 47,respectively, in the base member 22.

During normal operation while the priming pump is not in use, the springlock 27 secures the knob 26 and the plunger assembly 11 in place withinthe pump as shown in FIG. 1. To prime an engine with fuel prior tostartup, the spring lock 27 is released and the plunger assembly 11 ismanually moved in reciprocable motion by means of the knob 26. As thepiston 13 is raised within the cylinder 12 from its position shown inFIG. 1, presme in the lower chambers 23 tends to decrease while iuidpressure in the upper chamber 24 tends to increase. lhe decreasingpressure in chamber 23 causes the inlet :heck valve 38 to open whilemaintaining the outlet check valve 41 in a closed position. Fuel in theinlet passage 36 is then permitted to flow into and fill the chamber 23.[he upper chamber 24 is normally filled with fuel while the pump is inthe position shown in FIG. 1. Simultaneausly with the pressure decreaseand filling of the lower :hamber 23, increasing pressure in the upperchamber 24 is communicated to the inlet check valve 39 and the autletcheck valve 42 by means of the annular passage 17 and the respectivepassages 46 and 47. The increased pressure closes the inlet valve 39 andopens the outlet valve 42 so that fuel from a chamber 24 is directed tothe passage 37 and the engine fuel system. As the plunger assembly 11completes its upward stroke and is then moved in a downward stroke,fluid which entered the lower chamber 23 during the upward pump strokeexperiences increasing pressure while the upper chamber 24 experiencesdecreasing pressure. The positions of the check valves are then reversedwith inlet valve 38 and outlet valve 42 being closed and inlet valve 39and outlet valve 41 being opened. During this downward stroke, fuel frompassage 36 is drawn through the annular passage 17 to fill the chamber24 while fuel from the lower chamber 23 is directed to the engine fuelsystem. This reciprocating operation of the pump is continued to rapidlydeliver an adequate amount of priming fuel to insure starting of theengine. Upon completion of the priming operation, the plunger assemblyis again secured within the pump by means of the spring lock 27.

What is claimed is:

1. A fluid priming pump comprising a pair of cylinders including wallsfree of ports, said cylinders comprising a first inner cylindersurrounded by a second larger diameter cylinder spaced therefrom and ofgreater length then said first cylinder to define an annular passagetherebetween, stepped plugs providing the sole support for saidcylinders, said stepped plugs inserted in the respective ends of saidcylinders, each said plug including a first surface in press fitengagement with the inner surface of an end portion of the outercylinder, a shoulder, and a smaller diameter extension terminating in anend within said first cylinder and including a cylindrical surface theextreme portion only of which is in press fit engagement with the innersurface of an end of the inner cylinder to leave an area of saidcylindrical surface between the end of said inner cylinder and saidshoulder exposed to said annular passage, one of said plugs including apassage in free communication between said exposed area and said end ofsaid plug, the other of said plugs including two sets of inlet and twosets of outlet passageways including check valves and arranged withinthe member, one of each set of said passageways communicating with saidexposed area and the other of each set communicating with the insertedend of said plug, a reciprocable piston arranged within the innercylinder and forming opposing chambers of oppositely varying volumeduring reciprocable motion of the piston, one of the chambers beingformed on one side of the piston by the one end of said inner cylinder,the other chamber being formed on the other side of the piston by theother end of the inner cylinder in combination with the annular passagewhereby substantially the entire internal volume of the two pistons isavailable for pumping operation, and rod means for operating the pistonin reciprocable motion, the rod means being secured to the piston andslidably extending, in sealed relation, through the plug.

References Cited UNITED STATES PATENTS 411,810 10/1889 Harwick 103-456586,736 7/1897 Diss 230188 2,174,805 10/1939 Raulerson 103156 3,142,25810/1965 Rutherford 103-175 3,185,042 5/1965 Hastings 103-216 FOREIGNPATENTS 283,004 1/ 1928 Great Britain.

575,916 4/ 1944 Great Britain. 1,003,400 3/ 1962 Great Britain.

WILLIAM L. FREEH, Primary Examiner US. Cl. X.R. 103216, 230218

